1. Field of the Invention
The present invention pertains to a medical device for use in therapy of a patient, and more particularly, pertains to a catheter for use in association with laser irradiation.
2. Description of the Prior Art
It is known in the art to use laser energy for medical purposes. A common medical application is in the ablation of tissue. For external use, the laser energy may be directly applied. However, when the procedure requires ablation of tissue which is not readily accessible, the use of a laser catheter is common. A typical application for a laser catheter is in the cardiovascular system. U.S. Pat. Nos. 4,997,431 and 4,985,028, both issued to Isner et al., show laser catheters particularly adapted for laser ablation within the cardiovascular system.
It is convenient to utilize a guide wire and or fixation wire in accordance with positioning and maintaining position of an ablation catheter. The above referenced patents issued to Isner et al., and incorporated herein by reference, teach the use of a wire for those purposes.
The ablation of tissue must be accomplished with great precision as the danger of also ablating necessary adjacent tissue is always present, especially when the process occurs remotely at the distal end of a relatively long catheter. U.S. Pat. No. 4,785,806 issued to Deckelbaum discusses a system whereby an attempt is made to distinguish different types of tissue using ultraviolet fluoroscopy. A similar approach is proposed in U.S. Pat. No. 4,718,417 issued to Kittrell et al. Spectral analysis of reflected light energy is also proposed in U.S. Pat. No. 4,669,467 issued to Willett et al.
However, none of these approaches monitors the operation of the ablation activity itself. It is the production and absorption of electromagnetic radiation producing controlled heating which actually ablates the unwanted tissue. The prior art discusses distinguishing the tissue prior to ablation and analyzing the products of the procedure following ablation, but none of the references measures the ablation activity directly during the heating process.